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%%% Copyright 2009 Andrew Thompson <andrew@hijacked.us>. All rights reserved.
%%%
%%% Redistribution and use in source and binary forms, with or without
%%% modification, are permitted provided that the following conditions are met:
%%%
%%% 1. Redistributions of source code must retain the above copyright notice,
%%% this list of conditions and the following disclaimer.
%%% 2. Redistributions in binary form must reproduce the above copyright
%%% notice, this list of conditions and the following disclaimer in the
%%% documentation and/or other materials provided with the distribution.
%%%
%%% THIS SOFTWARE IS PROVIDED BY THE FREEBSD PROJECT ``AS IS'' AND ANY EXPRESS OR
%%% IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
%%% MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
%%% EVENT SHALL THE FREEBSD PROJECT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
%%% INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
%%% (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
%%% LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
%%% ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
%%% (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
%%% SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
%% @doc Module with some general utility functions for SMTP.
-module(smtp_util).
-export([
mxlookup/1, guess_FQDN/0, compute_cram_digest/2, get_cram_string/1,
trim_crlf/1, rfc5322_timestamp/0, zone/0, generate_message_id/0,
generate_message_boundary/0]).
%% @doc returns a sorted list of mx servers for `Domain', lowest distance first
mxlookup(Domain) ->
case whereis(inet_db) of
P when is_pid(P) ->
ok;
_ ->
inet_db:start()
end,
case lists:keyfind(nameserver, 1, inet_db:get_rc()) of
false ->
% we got no nameservers configured, suck in resolv.conf
inet_config:do_load_resolv(os:type(), longnames);
_ ->
ok
end,
case inet_res:lookup(Domain, in, mx) of
[] ->
[];
Result ->
lists:sort(fun({Pref, _Name}, {Pref2, _Name2}) -> Pref =< Pref2 end, Result)
end.
%% @doc guess the current host's fully qualified domain name
guess_FQDN() ->
{ok, Hostname} = inet:gethostname(),
{ok, Hostent} = inet:gethostbyname(Hostname),
{hostent, FQDN, _Aliases, inet, _, _Addresses} = Hostent,
FQDN.
%% @doc Compute the CRAM digest of `Key' and `Data'
-spec(compute_cram_digest/2 :: (Key :: binary(), Data :: string()) -> binary()).
compute_cram_digest(Key, Data) ->
Bin = crypto:md5_mac(Key, Data),
list_to_binary([io_lib:format("~2.16.0b", [X]) || <<X>> <= Bin]).
%% @doc Generate a seed string for CRAM.
-spec(get_cram_string/1 :: (Hostname :: string()) -> string()).
get_cram_string(Hostname) ->
binary_to_list(base64:encode(lists:flatten(io_lib:format("<~B.~B@~s>", [crypto:rand_uniform(0, 4294967295), crypto:rand_uniform(0, 4294967295), Hostname])))).
%% @doc Trim \r\n from `String'
-spec(trim_crlf/1 :: (String :: string()) -> string()).
trim_crlf(String) ->
string:strip(string:strip(String, right, $\n), right, $\r).
-define(DAYS, ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]).
-define(MONTHS, ["Jan", "Feb", "Mar", "Apr", "May", "Jun",
"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]).
%% @doc Generate a RFC 5322 timestamp based on the current time
rfc5322_timestamp() ->
{{Year, Month, Day}, {Hour, Minute, Second}} = calendar:local_time(),
NDay = calendar:day_of_the_week(Year, Month, Day),
DoW = lists:nth(NDay, ?DAYS),
MoY = lists:nth(Month, ?MONTHS),
io_lib:format("~s, ~b ~s ~b ~2..0b:~2..0b:~2..0b ~s", [DoW, Day, MoY, Year, Hour, Minute, Second, zone()]).
%% @doc Calculate the current timezone and format it like -0400. Borrowed from YAWS.
zone() ->
Time = erlang:universaltime(),
LocalTime = calendar:universal_time_to_local_time(Time),
DiffSecs = calendar:datetime_to_gregorian_seconds(LocalTime) -
calendar:datetime_to_gregorian_seconds(Time),
zone((DiffSecs/3600)*100).
%% Ugly reformatting code to get times like +0000 and -1300
zone(Val) when Val < 0 ->
io_lib:format("-~4..0w", [trunc(abs(Val))]);
zone(Val) when Val >= 0 ->
io_lib:format("+~4..0w", [trunc(abs(Val))]).
%% @doc Generate a unique message ID
generate_message_id() ->
FQDN = guess_FQDN(),
Md5 = [io_lib:format("~2.16.0b", [X]) || <<X>> <= erlang:md5(term_to_binary([erlang:now(), FQDN]))],
io_lib:format("<~s@~s>", [Md5, FQDN]).
%% @doc Generate a unique MIME message boundary
generate_message_boundary() ->
FQDN = guess_FQDN(),
["_=", [io_lib:format("~2.36.0b", [X]) || <<X>> <= erlang:md5(term_to_binary([erlang:now(), FQDN]))], "=_"].
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